Ball mill



y 8, 1969 o. ENGLER 3,454,231

BALL MILL Filed July 22, 1965 Fl6.l.

INVENTOR.

United States Patent 3,454,231 BALL MILL Otto Engler, Dusseldorf, Germany, assignor to Vereinigte Kesselwerke Aktiengesellschaft, Dusseldorf, Germany Filed July 22, 1965, Ser. No. 474,087 Int. Cl. B02c 15/12 U.S. Cl. 241-103 6 Claims ABSTRACT OF THE DISCLOSURE A ball and pan mill, including a pan mounted for rotation about a substantially vertical axis and having an upper end face provided with a concentric annular groove, drive means for rotating the pan, a plurality of equidistant balls having lower portions extending into the groove, biasing means engaging the upper portions of and arranged to press the balls against the pan, and spacer means including a carrier concentric with and rotatably mounted on the pan intermediate the groove and the biasing means, and a pair of arms extending outwardly from the carrier between each pair of adjoining balls, each of the arms engaging the median portion of the nearest ball so that each such ball is held between two arms.

The present invention relates to grinding or comminuting apparatus in general, and more particularly to apparatus of the type known as ball mills. Still more particularly, the invention relates to improvements in ball mills of the class wherein a series of pulverizing or comminuting balls cooperate with a driven pan to crush solid granular material which is admitted into their path. Such ball and pan mills may be utilized for pulverizing fragmentized coal or similar relatively hard materials.

It is already known to provide a grinding or pulveriz- 1 ing apparatus with a revolving pan and with a plurality of rollers which travel along the upper end face of the pan to thereby comminute coal or another solid granular material. Reference may be had to my U.S. Patent No. 2,689,689, granted Sept. 21, 1954, which discloses a revolving pan with three pulverizing rollers. It was found that, in using such apparatus, certain difiiculties arise in connection with the feed of material which is delivered from above and through the spaces between the rollers. The bearings and the supports for such rollers occupy considerable space and often interfere with proper feed of material. Also, the bearings and the supports for the rollers are rather complicated, and the rollers are not readily accessible.

Accordingly, it is an important object of my present invention to provide a very simple, sturdy, reliable, readily adjustable and versatile grinding apparatus which fully avoids the aforementioned drawbacks of presently known grinding apparatus and wherein the rolling elements which cooperate with the revolving pan do not unduly interfere with proper feed of material into the grinding or comminuting zone.

Another object of the invention is to provide a ball and pan mill wherein the rolling elements may be guided, spaced and their movements controlled in a very simple and convenient manner.

A further object of the invention is to provide a ball and pan mill of the just outlined characteristics with a novel spacer structure for the balls and to construct the spacer structure in a way to insure that all such parts thereof which undergo considerable wear are readily accessible and removable to be replaced by fresh parts with little loss in time.

An additional object of the invention is to provide a spacer structure of the just outlined characteristics wherein the position of ball-engaging elements may be adjusted once or more than once so that the useful life of such elements may be extended without in any way reducing the effectiveness of the mill.

Still another object of the invention is to provide a ball and pan mill wherein the spacer structure need not be driven, wherein such spacer structure occupies a minimum of space, wherein the spacer structure comprises a small number of parts, and wherein the spacer structure may be reached without necessitating complete dismantling of the remaining components of the mill.

Briefly stated, one feature of my invention resides in the provision of a ball and pan mill which comprises a stationary upright tubular housing wherein the material to be comminuted is fed from above, a pan mounted in the housing for rotation about a vertical axis and having an upper end face provided with a concentric annular groove, a plurality of equidistant balls having lower portions extending into the annular groove of the pan, drive.

means for rotating the pan whereby the balls roll along the groove to crush the material which is fed into the groove from above and descends onto the upper end face of the pan to move radially outwardly in response to rotation of the pan, biasing means engaging the upper portions of the balls to press such balls against the pan, and spacer means including a carrier which is concentric with and is rotatably mounted on the pan between the annular groove and the biasing means, and a pair of slender arms extending outwardly from the carrier between each pair of adjoining balls. Each arm engages the median or central portion of the nearest ball so that each ball is held between two arms. The arms may be provided with wear-resistant linears which come into actual engagement with the respective balls, and each such arm may be mounted on a pin so that it can be moved angularly about a vertical axis with reference to a projection extending radially outwardly from the carrier. In such mills, the spacer means further comprises suitable spreaders which are disposed between each pair of arms and are movable radially inwardly and outwardly or axially upwardly and downwardly to thereby change the angular position of the corresponding arms and to thus adjust the exact distance between the liners and the median portions of the nearest balls.

The carrier preferably resembles a cup which is rotatable on the upper end portion of a drive shaft for the pan, and such end portion extends upwardly and beyond the upper end face of the pan.

The novel features which are considered as charaacteristic of the invention are set forth in particular in the appended claims. The improved mill itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of a specific embodiment with reference to the accompanying drawings, in which:

FIG. 1' is a fragmentaryaxial section through a ball and pan mill which embodies my invention; and

FIG. 2 is a horizontal section substantially as seen in the direction of arrows from the line 11-11 of FIG. 1.

Referring to the drawings, there is shown a ball and pan mill which comprises a stationary upright tubular housing 1 which preferably resembles a hollow cylinder and accommodates a concentric pan 2 having an upper end face 2a provided with a concentric annular groove 3. The pan 2 is turnable about the vertical axis of the housing 1 and is rotated by a drive including a vertical shaft 9a. The upper end portion or stub S of the drive shaft 9a extends beyond the upper end face 2a of the pan 2 and .carries a cupped carrier 16 which is rotatable with reference thereto. The upper end portion 9 of the shaft 9a can be said to constitute a part of the pan 2, and the carrier 16 is rotatable with reference to the pan.

The groove 3 in the upper end face 2a accommodates the lower portions of three equidistant pulverizing balls 4 whose upper portions extend into and are guided by the surface surrounding an annular groove 5 provided in the lower end face of a vertically reciprocable annular biasing member 5a accommodated in the housing 1 at a level above the pan 2 and surrounding the carrier 16 with at least some clearance. The biasing member 5a is provided with a vertically extending peripheral cutout 5b which receives a guide rail or key 6 fixed to the housing 1 and allowing the member 5a to move up and down in response to and against the bias of several prestressed elements here shown as helical springs 7. The rail 6 holds the biasing member 5a against rotation with reference to the housing 1. The uppermost convolution of each spring 7 bears against a stationary biasing member 8 which is of annular shape and is rigidly but vertically adjustably secured to the housing 1. The periphery of the biasing member 8 is also provided with a vertical cutout 8a which receives a fixed guide rail or key 8b so as to allow for vertical adjustments of the member 8 with reference to the housing 1. The means for allowing such adjustments may comprise one or more radially inwardly extending screws which engage the member 8 to hold it in the axial position of FIG. 1. When the screws are loosened, the member 8 may be adjusted up or down to relax or to increase the bias of the springs 7. The parts 5a, 7 and 8 together constitute a biasing means serving to press the lower portions of the balls 4 against the pan 2.

In accordance with an important feature of my invention, the carrier 16 forms part of a star-shaped spacer structure for the balls 4, and this spacer structure further includes three radially outwardly extending projections or lugs 10 each of which is located midway between two balls 4. The outer ends of the projections 10 carry pairs of outwardly diverging arms 17 which are movable angularly about vertical pivot pins 12, and each arm 17 is provided with a wear-resistant liner 11 which may engage the median or central portion of the nearest ball 4. Thus each ball is held between two liners 11.

The spacer means of my improved mill further comprises spreaders in the form of wedges 13' which are movable radially toward and away from the axis of the housing 1 to thereby change the mutual inclination of the respective pairs of arms 17. Thus, if the wedges 13 are moved toward the axis of the end portion 9, the respective pairs of arms 17 will move further away from each other and their liners 11 will be placed nearer to the adjoining balls 4. The means for allowing such adjustment of the spreaders 13 may comprise radially extending spindles 13a which are rotatable in the respective projections 10 or directly in the carrier 16 and which extend through tapped bores provided in the respective spreaders. Thus, when a spindle 13a is rotated about its own axis, the corresponding spreader 13 will move toward or away from the corresponding projection 10 and will change the mutual inclination of the corresponding arms 17 and liners 11.

The housing 1 is mounted on a suitable base, not shown, which also supports the remaining components of the drive for the pan 2. The lower part of the housing 1 further accommodates a suitable blower which produces an ascending current of air serving to carry the pulverized material toward and beyond the upper end of the housing. Material to be pulverized is admitted through the annular biasing members 8 and 5a and descends onto the upper end face 2a of the revolving pan 2 within the confines of the groove 3. Such material is carried radially outwardly by centrifugal force and enters the groove 3 wherein it undergoes a comminuting action in response to engagement with the balls 4 which roll along the groove 3 whenever the pan 2 rotates. The thus pulverized material is propelled upwardly to a further station or directly to the locale of actual use. For example, the mill may be used for pulverizing coal, and the resulting pulverulent material may be fed to one or more burners which are specifically constructed to combust pulverulent fuel. One or more sieves for pulverulent material may be installed in the housing 1 at a level above the biasing means.

FIG. 2 shows that the carrier 16, the projections 10, the arms 17, their liners 11 and the balls 4 define between themselves three spaces or passages 20 of relatively large area so as to provide ample room for descent of coal or other granular material which is pulverized on entry into the groove 3. The arms 17 and their liners 11 are located in a plane which is common to the centers of the balls 4 so that the liners 11 engage the balls midway between the grooves 3 and 5. The liners 11 are readily detachable so that, when necessary, each thereof may be replaced with a fresh liner. However, prior to such replacement, each of the liners 11 may be adjusted once or more than once, and such adjustment may be carried out by means of the spreaders 13 and their spindles 13a so that the useful life of each liner is a multiple of the useful life of a liner on a rigidly mounted arm. It is clear that the pairs of arms 17 may be made to move toward or away from each other in response to vertical movement of the spreaders 13. Adjustments in the angular position of the arms 17 and/or replacement of the liners 11 will necessitate only short-lasting interruptions in the operation of the mill.

It is further clear that each of the arms 17 may be mounted on a separate pivot 12, and that the wedgeshaped spreaders 13 may be replaced with different types of spreading devices. Such spreading devices insure that the liners 11 remain in proper positions with reference to the adjoining balls 4, preferably with a certain amount of play to prevent excessive wear. The balls 4 have identical diameters.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of my contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is:

1. In a ball and pan mill, a pan mounted for rotation about a substantially vertical axis and having an upper end face provided with a concentric annular groove; drive means for rotating said pan; a plurality of equidistant balls having lower portions extending into said groove; biasing means engaging the upper portions of said balls and arranged to press the lower portions of such balls against said pan; and spacer means including a carrier concentric with and rotatably mounted on said pan intermediate said groove and said biasing means, a plurality of equidistant projections extending radially outwardly from said carrier and each located midway between a pair of balls, a pair of outwardly diverging arms pivotally secured to each of said projections for angular movement about axes which are parallel to said vertical axis, each of said arms engaging the median portion of the nearest ball so that each such ball is held between two arms, and spreader means disposed between the arms of each of said pairs of arms and adjustably secured to said carried so as to allow for changes in mutual inclination of the respective arms.

2. In a ball and pan mill, a pan mounted for rotation about a substantially vertical axis and having an upper end face provided with a concentric annular groove; drive means for rotating said pan; a plurality of equidistant balls having lower portions extending into said groove; biasing means engaging the upper portions of said balls and arranged to press the lower portions of such balls against said pan; and spacer means including a carrier concentric with and rotatably mounted on said pan intermediate said groove and said biasing means, a plurality of equidistant projections extending radially outwardly from said carrier and each located midway be tween a pair of balls, a pair of outwardly diverging arms pivotally secured to each of said projections for angular movement about axes which are parallel to said vertical axis, each of said arms engaging the median portion of the nearest ball so that each such ball is held between two arms, and a wedge-like spreader disposed between the arms of each of said pairs of arms and supported by said carrier for movement radially of said vertical axis to change the mutual inclination of the respective arms.

3. In a ball and pan mill, a pan rotatable about a vertical axis and having an upper end face provided with a concentric groove; drive means for said pan including a vertical shaft having an upper end portion extending beyond said upper end face; three equidistant balls having lower portions extending into said groove; biasing means engaging the upper portions of and arranged to press said balls against said pan; and spacer means including a cupped carrier rotatably supported by and surrounding the upper end portion of said shaft, three radially outwardly extending projections rigid with said carrier and each located midway between a pair of balls, a pair of outwardly diverging arms pivotally secured to each of said projections for angular movementabout vertical axes, each of said arms comprising a liner engaging the nearest ball so that each such ball is held between two liners, and a wedge-shaped spreader disposed between the arms of each of said pairs of arms, each of said spreaders being adjustable in directions radially toward and away from the axis of said pan to thereby adjust the mutual inclination of said arms and to move said liners in requisite position with reference to the nearest balls.

4. In a ball and pan mill, an upright cylindrical housing; a pan concentrically mounted in said housing and rotatable about a vertical axis, said pan having an upper end face provided with a concentric annular groove; drive means for rotating said pan including a vertical shaft having an upper end portion extending upwardly and beyond said upper end face; a plurality of equidistant balls having lower portions extending into said groove; biasing means for pressing the balls against said pan, including a stationary member secured to said housing at a level above said balls, a vertically reciprocable member located below said stationary member and having a lower end face provided with an annular groove receiving the upper portions of said balls, and at least one prestressed resilient element disposed between said members; and spacer means including a cupped carrier rotatably surrounding the end portion of said shaft, a plurality of equidistant projections extending radially outwardly from said carrier and each located midway between a pair of balls, a pair of outwardly diverging arms pivotally secured to each of said projections for angular movement about vertical axes and each having a liner engaging the central portion of the nearest ball so that each of said balls is held between two arms, and spreader means for changing the mutual inclination of the arms of each of said pairs of arms.

5. A structure as set forth in claim 4, wherein the number of said balls exceeds two and wherein said spacer means and said balls define between themselves relatively large vertically extending passages through which a material which is to be comminuted may be fed onto the upper end face of said pan within the confines of said first mentioned annular groove.

6. In a ball and pan mill, a spacer structure including a cupper carrier rotatable about a fixed axis; a plurality of equidistant projections extending radially outwardly from said carrier; a pair of outwardly diverging arms pivotally secured to each of said projections so as to be movable angularly about axes which are parallel with said fixed axis; a wear-resistant liner detachably secured to each of said arms; and an adjustable spreader provided between the arms of each of said pairs of arms and arranged to change the angular positions of the respective arms.

References Cited UNITED STATES PATENTS 276,145 4/1883 Rogers 241-103 318,117 5/1885 Huntington 241103 515,453 2/ 1894 Tornaghi 241103 581,755 5/1897 Norris 241103 584,086 6/1897' Woods 24l103 584,980 6/1897 Best 24l103 615,278 12/1898 Johnson 241-l03 657,933 9/ 1900 Gath 241104 955,910 4/1910 Sackett 241103 1,401,716 12/1921 McCrae 241104 2,879,006 3/ 1959 Clements -1 241119 3,093,327 6/1963 Harvey 24l-103 ROBERT C. RIORDON, Primary Examiner.

D. G. KELLY, Assistant Examiner. 

